Respiratory consequences of preterm birth

Approximately 8% of Australia's 250 000 annual births occur preterm (before 37 weeks completed gestation). Preterm infants represent 75% of all neonatal deaths in Australia, with the vast majority of these deaths caused by pulmonary disease. The respiratory consequences for survivors of preterm birth include the immediate challenges of breathing with underdeveloped lungs, usually manifest as respiratory distress syndrome (RDS), and, in the long term, with persisting pulmonary abnormalities. Therapies to prevent neonatal lung disease now permit survival of preterm infants born as early as 22 weeks gestational age, but not without consequences. Preterm infants are at risk of developing chronic lung disease/bronchopulmonary dysplasia (BPD). The lungs of infants dying from BPD are inflamed and have fewer, larger alveoli than normal and exhibit abnormal pulmonary vascular development. There is now a growing appreciation of the contribution of intrauterine inflammation to the aetiology of BPD. Impaired airway function is commonly reported in follow-up studies of children born preterm. Decreased expiratory flow rates have been associated with preterm birth per se, but airway function appears more affected in survivors of RDS and BPD. Observations in survivors of BPD suggest persisting abnormalities in the structure of the lung parenchyma and airways. Follow-up studies of preterm infants into adulthood are lacking, as are experimental examinations of the long-term physiological and anatomical effects of preterm birth. Both are necessary to understand the causes of the long-term respiratory consequences of preterm birth.